SoundTouch is an open-source audio processing library for changing the
Tempo, Pitch and Playback Rates of audio streams or files:
 * Tempo (time-stretch): changes the sound to play at faster or slower
 speed than original, without affecting the sound pitch
 * Pitch (key): changes the sound pitch or key, without affecting the
 sound tempo or speed
 * Playback Rate: changes both the sound tempo and pitch, as if an LP
 disc was played at wrong RPM rate
